Prosthetic heart valve with retention elements

ABSTRACT

Described embodiments are directed toward centrally-opening leaflet prosthetic valve devices having a leaflet frame and a leaflet construct. The leaflet construct is at least partially coupled to a leaflet frame outer side of the leaflet frame and being coupled thereto by a retention element.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.16/446,343, filed Jun. 19, 2019, which is a continuation of U.S. patentapplication Ser. No. 15/791,562, filed Oct. 24, 2017, now U.S. Pat. No.10,342,659, issued Jul. 9, 2019, which is a continuation of U.S. patentapplication Ser. No. 14/853,654, filed Sep. 14, 2015, now U.S. Pat. No.9,827,094, issued Nov. 28, 2017, which claims the benefit of U.S.Provisional Application 62/050,628, filed Sep. 15, 2014, all of whichare incorporated herein by reference in their entireties for allpurposes.

FIELD

The present disclosure relates generally to prosthetic valves and morespecifically flexible leaflet-type prosthetic heart valve devices.

BACKGROUND

A number of fabrication techniques have been used to couple the leafletsto a frame, including sewing individual leaflets to the frame(biological and synthetic), and for synthetic leaflets only, injectionmolding and dip coating a polymer onto the frame. In many cases, theresulting leaflet is supported on the frame and defines a flap having amounting edge where the leaflet is coupled to the frame and a free edgethat allows the flap to move. The flap moves under the influence offluid pressure. In operation, the leaflets open when the upstream fluidpressure exceeds the downstream fluid pressure and closes when thedownstream fluid pressure exceeds the upstream fluid pressure. The freeedges of the leaflets coapt under the influence of downstream fluidpressure, closing the valve to prevent downstream blood from flowingretrograde through the valve.

Valve durability under the repetitive loads of the leaflets opening andclosing is dependent, in part, on the load distribution between theleaflet and the frame. Further, substantial load is encountered on theleaflet when in the closed position. Mechanical failure of the leafletcan arise, for example, at the mounting edge, where the flexible leafletis supported by the relatively rigid frame, particularly at thecommissure posts. The repetitive loads of leaflet opening and closingleads to material failure by fatigue, creep or other mechanism,depending in part on the leaflet material. Mechanical failure at themounting edge is especially prevalent with synthetic leaflets.

There remains a need for a more durable flexible leaflet prostheticvalve.

SUMMARY

Described embodiments are directed to apparatus, system, and methods forvalve replacement, such as cardiac valve replacement. More specifically,described embodiments are directed toward flexible leaflet valve deviceshaving biological or synthetic leaflet material and a frame, and methodsof making and implanting the valve devices.

According to an embodiment, a prosthetic heart valve comprises a leafletframe assembly. The leaflet frame assembly is an assembly of a leafletframe, leaflet construct, and retention elements. The leaflet constructis that portion of the valve that comprises the leaflets and thestructure for coupling the leaflets to the leaflet frame. In accordancewith an embodiment, the leaflet construct defines a contiguous annularring defining a plurality of leaflets and a bridge region between eachof the leaflets. Each bridge region defines a bridge first end adjacenta first leaflet and a bridge second end adjacent a second leaflet. Theleaflets extend radially inward from the leaflet frame when coupled tothe leaflet frame. Each of the leaflets defines a fold-over portion thatis folded over and lies against a leaflet frame outer side of theleaflet frame and coupled thereto such as with a securement structure,such as, but not limited to suture, adhesive, thermal bonding, or othermeans. Each of the bridge regions defines a bridge loop with acoaptation neck between the bridge loop and the adjacent leaflets. Thecoaptation neck is operable to pass through one of the post slots sothat the bridge loop is adjacent to the outer portion of the leafletframe and the leaflets extend radially inward from the leaflet frame. Aretention element is disposed within the bridge loop effectivelypreventing the bridge loop from passing through the post slot. Theretention element may be coupled to the commissure post, such as with asecurement structure, such as, but not limited to suture, adhesive,thermal bonding, or other means. The fold-over portion of each of theleaflets is folded around an inflow edge of the leaflet frame andcoupled thereto, such as with a securement structure, such as, but notlimited to suture, adhesive, thermal bonding, or other means.

A method of making a prosthetic valve, in accordance with an embodiment,comprises obtaining a tube comprising one or more layers of expandedPTFE composite. Cutting a leaflet construct including a plurality ofleaflets each being separated by a bridge region from the tube.Providing fold-over apertures in fold-over portions of the leaflets andbridge apertures in the bridge region. Obtaining a plurality ofretention elements, each retention element defining retention elementapertures. Folding each of the bridge regions into a bridge loop anddefining a coaptation neck between each bridge loop and two adjacentleaflets, the bridge loops extending radially away from the tube axis.Disposing a retention element into each of the bridge loops. Suturingeach retention element to the respective bridge loop passing suturethrough the bridge apertures and the retention element apertures thatare aligned therewith. Cutting a leaflet frame from a metal tubedefining leaflet frame windows and commissure posts therebetween whereeach commissure post defines a post slot dimensioned to receive a doublethickness of the bridge region. Providing leaflet window frame aperturesin the leaflet window frame and post apertures in the commissure posts.Disposing each coaptation neck in a respective post slot with theretention elements adjacent the post outer side and disposing theleaflets in the leaflet frame. Aligning the retention element apertureswith the post apertures. Suturing each retention element to therespective commissure post passing suture through the retention elementapertures and the post apertures that are aligned therewith. Folding thefold-over portions of each leaflet along the leaflet frame inflow edgeand against the leaflet frame outer side aligning the fold-overapertures with the leaflet window frame apertures. And suturing eachfold-over portion to the respective leaflet window frame passing suturethrough the fold-over apertures and the leaflet window frame aperturesthat are aligned therewith.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure and are incorporated in andconstitute a part of this specification, illustrate embodimentsdescribed herein, and together with the description serve to explain theprinciples discussed in this disclosure.

FIG. 1A is an outflow side perspective view of a prosthetic heart valvein accordance with an embodiment;

FIG. 1B is an inflow side perspective view of the embodiment of thevalve of FIG. 1A;

FIG. 2 is a perspective view of a leaflet frame assembly of theembodiment of the valve of FIG. 1A;

FIG. 3 is a side exploded view of the leaflet frame, retention element,leaflet construct and base frame, of an embodiment of a valve;

FIG. 4 is a representation of the embodiment of the valve of FIG. 3unrolled to a flat orientation, in accordance with an embodiment;

FIG. 5A is a perspective view of the bridge region formed into a bridgeloop, in accordance with the embodiment of FIG. 2 ;

FIG. 5B is a perspective view of the bridge region formed into a bridgeloop and containing a retention element, in accordance with theembodiment of FIG. 2 ;

FIG. 6 is a side view of the bridge region of the embodiment of FIG. 7 ;

FIG. 7 is a perspective view of a leaflet frame assembly and a baseframe, in accordance with the embodiment of the valve of FIG. 1A; and

FIG. 8 is a side view of the bridge region showing fold line at an anglealpha, in accordance with another embodiment.

DETAILED DESCRIPTION

Persons skilled in the art will readily appreciate that various aspectsof the present disclosure can be realized by any number of methods andapparatus configured to perform the intended functions. Stateddifferently, other methods and apparatus can be incorporated herein toperform the intended functions. It should also be noted that theaccompanying drawing figures referred to herein are not necessarilydrawn to scale, but may be exaggerated to illustrate various aspects ofthe present disclosure, and in that regard, the drawing figures shouldnot be construed as limiting.

Although the embodiments herein may be described in connection withvarious principles and beliefs, the described embodiments should not bebound by theory. For example, embodiments are described herein inconnection with prosthetic valves, more specifically cardiac prostheticvalves. However, embodiments within the scope of this disclosure can beapplied toward any valve or mechanism of similar structure and/orfunction. Furthermore, embodiments within the scope of this disclosurecan be applied in non-cardiac applications.

The term leaflet as used herein in the context of prosthetic valves is aflexible component of a one-way valve wherein the leaflet is operable tomove between an open and closed position under the influence of apressure differential. In an open position, the leaflet allows blood toflow through the valve. In a closed position, the leaflet substantiallyblocks retrograde flow through the valve. In embodiments comprisingmultiple leaflets, each leaflet cooperates with at least one neighboringleaflet to block the retrograde flow of blood. The pressure differentialin the blood is caused, for example, by the contraction of a ventricleor atrium of the heart, such pressure differential typically resultingfrom a fluid pressure building up on one side of the leaflets whenclosed. As the pressure on an inflow side of the valve rises above thepressure on the outflow side of the valve, the leaflets open and bloodflows therethrough. As blood flows through the valve into a neighboringchamber or blood vessel, the pressure on the inflow side equalizes withthe pressure on the outflow side. As the pressure on the outflow side ofthe valve raises above the blood pressure on the inflow side of thevalve, the leaflet returns to the closed position generally preventingretrograde flow of blood through the valve.

The term membrane as used herein refers to a sheet comprising a singlematerial, such as, but not limited to, expanded fluoropolymer.

The term composite material as used herein refers to a combination of amembrane, such as, but not limited to, expanded fluoropolymer, and anelastomer, such as, but not limited to, a fluoroelastomer. The elastomercan be contained within a porous structure of the membrane, coated onone or both sides of the membrane, or a combination of coated on andcontained within the membrane.

The term laminate as used herein refers to multiple layers of membrane,composite material, or other materials, such as elastomer, andcombinations thereof.

The term film as used herein generically refers to one or more of themembrane, composite material, or laminate.

The term biocompatible material as used herein generically refers to anymaterial with biocompatible characteristics including synthetic, suchas, but not limited to, a biocompatible polymer, or a biologicalmaterial, such as, but not limited to, bovine pericardium.

The terms native valve orifice and tissue orifice refer to an anatomicalstructure into which a prosthetic valve can be placed. Such anatomicalstructure includes, but is not limited to, a location wherein a cardiacvalve may or may not have been surgically removed. It is understood thatother anatomical structures that can receive a prosthetic valve include,but are not limited to, veins, arteries, ducts and shunts. It is furtherunderstood that a valve orifice or implant site may also refer to alocation in a synthetic or biological conduit that may receive a valve.

As used herein, “couple” means to join, connect, attach, adhere, affix,or bond, whether directly or indirectly, and whether permanently ortemporarily.

Embodiments herein include various apparatus, systems, and methods for aprosthetic valve, such as, but not limited to, cardiac valvereplacement. The valve is operable as a one-way valve wherein the valvedefines a valve orifice into which leaflets open to permit flow andclose so as to occlude the valve orifice and prevent flow in response todifferential fluid pressure.

FIGS. 1A and 1B are outflow and inflow, respectfully, perspective viewsof a valve 100 in the form of a prosthetic heart valve, in accordancewith an embodiment. The components of the valve 100 that are visible inFIGS. 1A and 1B include three flexible leaflets 310, a leaflet frame 200including three commissure posts 210 that has been covered with variousmaterial, a base frame 500 that has been covered with various material,and a sewing cuff 600. The leaflet free edges 312 of the leaflets 310come together at a cooptation region 316 in a Y-shaped pattern (whenviewed from above) to close the valve 100. The valve 100 closes in thisfashion when the pressure of the blood on the outflow side (as viewed inFIG. 1A) is greater than the pressure of the blood on the inflow side ofthe valve (as viewed in FIG. 1B). The leaflet free edges 312 of theleaflets 310 move apart to open the valve 100 and to let blood flowthrough the valve 100 from the inflow side as viewed in FIG. 1B when thepressure of the blood on the inflow side of the valve 100 is greaterthan the pressure on the outflow side of the valve 100.

FIGS. 2-5B show various components that are included in the valve 100,in accordance with an embodiment.

FIG. 2 is a perspective view of a leaflet frame assembly 234, inaccordance with an embodiment, also shown in FIG. 3 in an exploded viewand shown in FIG. 4 in an exploded view wherein the annular componentshave been longitudinally cut and laid open, so as to better illustratethe elements of the valve components. The leaflet frame assembly 234comprises a leaflet frame 200, a leaflet construct 300, and a pluralityof retention elements 400.

Leaflet Frame

The leaflet frame 200 is operable to hold and support the leafletconstruct 300. The leaflet frame 200 is annular, that is it defines acylinder having an axis X and a plurality of commissure posts 210extending parallel to the axis x that are spaced from one another, eachcommissure post 210 defining a post slot 217 therethrough that isaligned parallel to the axis X. Between the commissure posts 210 is aleaflet window 222 that is operable to couple to and support the leaflet310 around the perimeter of the leaflet 310 except for the leaflet freeedge 312.

The leaflet frame 200 defines a cylinder having a leaflet frame innerside 202 and a leaflet frame outer side 204 opposite the leaflet frameinner side 202. The leaflet frame 200 further defines a plurality ofcommissure posts 210. Each commissure post 210 has a post outer side 212and a post inner side 214 opposite the post outer side 212. Thecommissure post 210 is defined by a first post leg 216 and a second postleg 218 separated by a post slot 217 therebetween. A commissure tip 219couples the first post leg 216 and the second post leg 218.

In accordance with an embodiment, the leaflet frame 200 is annular abouta central longitudinal axis X of the valve 100 as shown in FIGS. 2 and 3. The leaflet frame 200 defines a plurality of leaflet windows 222 thatfollow the shape of the leaflet 310. In accordance with an embodiment,each of the leaflet windows 222 includes two leaflet window sides 223and a leaflet window base 225, defining three sides of an isoscelestrapezoid, wherein the leaflet window base 225 is substantially flat.The leaflet base 325 is coupled to the leaflet window base 225 and eachof the two leaflet sides 323 are coupled to one of the two leafletwindow sides 223. The adjacent leaflet window sides 223 areinterconnected by a commissure post 210 comprising of a first post leg216 and a second post leg 218 that extend from adjacent leaflet windowsides 223 and meet at a commissure tip 219. The commissure posts 210 areequally spaced from one another around the leaflet frame 200. The firstpost leg 216 and the second post leg 218 define a post slot 217therebetween.

The leaflet frame 200 can be etched, cut, laser cut, stamped,three-dimensional printed, among other suitable processes, into anannular structure or a sheet of material, with the sheet then formedinto an annular structure.

The leaflet frame 200 can comprise, such as, but not limited to, anyelastically deformable metallic or polymeric material that is generallybiocompatible. The leaflet frame 200 can comprise a shape-memorymaterial, such as nitinol, a nickel-titanium alloy. Other materialssuitable for the leaflet frame 200 include, but not limited to, othertitanium alloys, stainless steel, cobalt-nickel alloy, polypropylene,acetyl homopolymer, acetyl copolymer, other alloys or polymers, or anyother material that is generally biocompatible having adequate physicaland mechanical properties to function as a leaflet frame 200 asdescribed herein.

Leaflet Construct

The leaflet construct 300 is that portion of the valve 100 thatcomprises the leaflets 310 and the structure for coupling the leaflets310 to the leaflet frame 200. In accordance with an embodiment, theleaflet construct 300 defines a contiguous annular ring defining aplurality of leaflets 310 and a bridge region 330 between each of theleaflets 310. As used herein, contiguous means without a break or aseam, that is, seamless. Each bridge region defines a bridge first end332 adjacent a first leaflet 310 and a bridge second end 334 adjacent asecond leaflet 310. The leaflets extend radially inward from the leafletframe 200 when coupled to the leaflet frame 200. Each of the leaflets310 define a fold-over portion 324 that is folded over and lies againsta leaflet frame outer side 204 of the leaflet frame 200 and coupledthereto. Each of the bridge regions 330 defines a bridge loop 338 with acoaptation neck 340 between the bridge loop 338 and the adjacentleaflets 310. The coaptation neck 340 is operable to pass through one ofthe post slots 217 so that the bridge loop 338 is adjacent to the outerportion of the leaflet frame 200 and the leaflets 310 extend radiallyinward from the leaflet frame 200.

The leaflet construct 300 comprising the flexible leaflets 310 can bemade of polymer. For example, pre-shaped polymer leaflets can be made bystarting from a cylinder of polymer material that has been cut into ashape like that shown in FIGS. 3 and 4 .

The leaflet construct 300 can also be made from a sheet of polymermaterial that has been cut into a shape like that shown in FIGS. 3 and 4and subsequently coupled together into an annular shape. A leafletconstruct 300 having a seam, though may not have the advantages of acontiguous, seamless construct that may exhibit a higher tensilestrength characteristics. The advantages provided by the retentionelement 400 may still be realized.

Another way that the leaflet construct 300 may be formed (assuming theuse of a material for the leaflets that is suitable for formation inthis way) is by compression or injection molding.

In accordance with an embodiment, each leaflet 310, at the folds 326,has substantially the shape of an isosceles trapezoid having two leafletsides 323, a leaflet base 325 and a leaflet free edge 312 opposite theleaflet base 325, corresponding to the two leaflet window sides 223 anda leaflet window base 225. The two leaflet sides 323 diverge from theleaflet base 325, wherein the leaflet base 325 is substantially flat.

In accordance with other embodiments of the valve 100, each leaflet 310includes a central region 329 and two side regions 328 on opposite sidesof the central region 329. The central region 329 is defined by a shapesubstantially that of an isosceles trapezoid defined by two centralregion sides 327, the leaflet base 325 and the leaflet free edge 312.Each of the side regions 328 has a shape substantially that of atriangle and each are defined by one of the central region sides 327,one of the leaflet sides 323, and the leaflet free edge 312.

In accordance with another embodiment, the leaflet window may bedescribed as having a U-shape. The leaflet frame generally defines aplurality of U-shaped portions as one proceeds annularly around theleaflet frame, defining a plurality of commissure posts and a pluralityof leaflet window frame portions.

As shown in FIG. 4 , each of the leaflets 310 has a leaflet bellyportion 322, and a fold-over portion 324. The leaflet belly portion 322of each leaflet 310 is the operating portion of the leaflet 310 when ina finished and implanted valve 100. The fold-over portion 324 of eachleaflet 310 is the portion that is used to secure the leaflet 310 to thetwo leaflet window sides 223 and the leaflet window base 225 of theleaflet frame 200. Each leaflet window side 223 and a leaflet windowbase 225 of the leaflet frame 200 fits into a fold 326 that is formedbetween the leaflet belly portion 322 and the fold-over portion 324 of arespective one of the leaflet sides 323 and leaflet base 325,respectively, of the leaflets 310, as shown in FIG. 2 . The leafletbelly portion 322 of each leaflet 310 includes enough material betweenthe commissure posts 210 of the leaflet frame 200 so that the leafletfree edge 312 of the three leaflet belly portions 322 can come togetheror coapt in the interior of the valve 100 to close the valve 100 asshown in FIG. 1 .

Between each of the leaflets 310 is a bridge region 330, as shown inFIGS. 4, 5A, 5B and 8 . The bridge region 330 is operable to be formedinto a bridge loop 338 having a generally rectangular shape, foldingabout two loop fold lines 336 so as to contain the retention element 400therein as discussed below, as shown in FIGS. 5A, 5B, 6 and 8 . Due tothe curvature of the annular leaflet frame 200, the two loop fold lines336 form an angle alpha, which corresponds to the retention elementsides 402 as shown in FIG. 6 , in accordance with an embodiment.

In accordance with an embodiment, the leaflet construct 300 can comprisea biocompatible material that is not of a biological source and that issufficiently compliant and strong for the particular purpose, such as abiocompatible polymer. In an embodiment, the leaflet construct 300comprises a membrane that is combined with an elastomer to form acomposite material. In accordance with other embodiments, thebiocompatible material that makes up the leaflet construct 300 comprisesa biological material, such as, but not limited to, bovine pericardium.

The shape of the leaflets 310 are defined in part by the shape of theleaflet frame 200 and the leaflet free edge 312. The shape of theleaflets 310 can also be defined by the structures and processes used tomanufacture the valve 100, such as, but not limited, those describedbelow. For example, in accordance with an embodiment, the shape of theleaflets 310 also depends in part on molding the leaflets 310 usingmolding and trimming processes to impart a predetermined shape to theleaflet 310.

The leaflets 310 generally flex about the leaflet base 325 about theleaflet window base 225 of the U-shaped portion as the leaflets 310 openand close. In an embodiment, when the valve 100 is closed, generallyabout half of each leaflet free edge 312 abuts an adjacent half of aleaflet free edge 312 of an adjacent leaflet 310, as shown in FIG. 1A.The three leaflets 310 of the embodiment of FIG. 1A meet at a triplepoint 348. The valve orifice 150 is occluded when the leaflets 310 arein the closed position stopping fluid flow.

Leaflet Construct Material

The leaflet construct 300 can comprise any biocompatible materialsufficiently compliant and flexible, such as a biocompatible polymer.The leaflet construct 300 can comprise a membrane that is combined withan elastomer to form a composite material. The leaflet construct 300 cancomprise, according to an embodiment, a composite material comprising anexpanded fluoropolymer membrane, which comprises a plurality of spaceswithin a matrix of fibrils, and an elastomeric material. It should beappreciated that multiple types of fluoropolymer membranes and multipletypes of elastomeric materials can be combined to form a compositematerial while remaining within the scope of the present disclosure. Itshould also be appreciated that the elastomeric material can includemultiple elastomers, multiple types of non-elastomeric components, suchas inorganic fillers, therapeutic agents, radiopaque markers, and thelike while remaining within the scope of the present disclosure.

In accordance with an embodiment, the composite material includes anexpanded fluoropolymer material made from porous ePTFE membrane, forinstance as generally described in U.S. Pat. No. 7,306,729 to Bacino.

The expandable fluoropolymer, used to form the expanded fluoropolymermaterial described, can comprise PTFE homopolymer. In alternativeembodiments, blends of PTFE, expandable modified PTFE and/or expandedcopolymers of PTFE can be used. Non-limiting examples of suitablefluoropolymer materials are described in, for example, U.S. Pat. No.5,708,044, to Branca, U.S. Pat. No. 6,541,589, to Baillie, U.S. Pat. No.7,531,611, to Sabol et al., U.S. patent application Ser. No. 11/906,877,to Ford, and U.S. patent application Ser. No. 12/410,050, to Xu et al.

The expanded fluoropolymer membrane can comprise any suitablemicrostructure, such as pores, for achieving the desired leafletperformance. Other biocompatible polymers which can be suitable for usein leaflet include but are not limited to the groups of urethanes,silicones (organopolysiloxanes), copolymers of silicon-urethane,styrene/isobutylene copolymers, polyisobutylene,polyethylene-co-poly(vinyl acetate), polyester copolymers, nyloncopolymers, fluorinated hydrocarbon polymers and copolymers or mixturesof each of the foregoing.

Further examples of leaflet construct materials include: wherein theleaflet construct comprises at least one fluoropolymer membrane layer;wherein the leaflet construct comprises a laminate having more than onefluoropolymer membrane layer; wherein the at least one fluoropolymermembrane layer is an expanded fluoropolymer membrane layer; wherein anelastomer is contained within the expanded fluoropolymer membrane layer;wherein the elastomer comprises perfluoromethyl vinyl ether andtetrafluoroethylene; wherein the expanded fluoropolymer membrane layercomprises ePTFE; wherein the leaflet construct comprises a compositematerial having at least one fluoropolymer membrane layer having aplurality of pores and an elastomer present in the pores of at least oneof the fluoropolymer membrane layers; wherein the composite materialcomprises fluoropolymer membrane by weight in a range of about 10% to90%; wherein the elastomer comprises (per)fluoroalkylvinylethers (PAVE);wherein the elastomer comprises a copolymer of tetrafluoroethylene andperfluoromethyl vinyl ether; wherein the elastomer is silicone; whereinthe elastomer is a fluoroelastomer; wherein the elastomer is a urethane;and wherein the elastomer is a TFE/PMVE copolymer; wherein the TFE/PMVEcopolymer comprises essentially of between about 40 and 80 weightpercent perfluoromethyl vinyl ether and complementally 60 and 20 weightpercent tetrafluoroethylene; and wherein the leaflet construct comprisessilicone.

Retention Element

The retention element 400 is an element that is operable to be disposedwithin the bridge loop 338 formed by the bridge region 330 of theleaflet construct 300, which effectively prevents the bridge loop 338from passing through the post slot 217, and therefore the leafletconstruct 300 is mechanically coupled to the commissure post at the postouter side. The retention element 400 has a width that is larger than awidth of the post slot 217. With the retention element 400 beingdisposed in the bridge loop 338, the bridge loop 338 will be preventedfrom passing through the post slot 217. The size of the bridge loop 338should correspond closely to the size of the retention element 400 toprevent a portion of the bridge region 330 from extending through thepost slot 217 to the valve orifice 150 in case of the suture looseningor failing.

In accordance with an embodiment, the retention element 400 defines arelatively flat generally rectangular shape so as to have a low profileon the post outer side 212 of the commissure post 210. Due to thecurvature of the annular leaflet frame 200, the sides of the retentionelement 400 are formed at an angle corresponding to the two loop foldlines 336 that form an angle alpha, as shown in FIG. 8 , in accordancewith an embodiment.

In accordance with embodiments, the retention element 400 can be flat,relatively flat, or concave on the inside (toward the center of thevalve) to correspond with the radially outer convexity of commissurepost 210 that the retention element 400 will be adjacent to. Eachretention element 400 has a plurality of retention element apertures 408that align with commissure post apertures 209 wherein the retentionelement 400 is placed against the post outer side 212 of the commissurepost 210 with a portion of the bridge region 330 therebetween. Asecurement structure, such as, but not limited to suture 700, may beused to couple the retention element 400 to the commissure post 210.Suture may be of any suitable material, such as PTFE, PET, and nylon,among others. Stitching comprising suture 700 may be passed throughthese aligned commissure post apertures 209 and retention elementapertures 408 and the bridge region 330 to hold each retention element400 and the bridge region 330 to the commissure post 210. Some or all ofthis suture 700 may pass through the fold-over portion 324 of theleaflet 310. In that event, this suture 700 will contribute to securingthe leaflet belly portion 322 of the leaflets 310 to the leaflet frame200.

Examples of suitable materials for the retention elements 400 includevarious biocompatible alloys such as titanium, Elgiloy, MP35N, stainlesssteel, nitinol, etc., and various biocompatible engineering plasticssuch as acetyl polymers, PTFE, and PEEK.

Leaflet Frame Assembly

A leaflet frame assembly 234 is the assembly of the leaflet frame 200,leaflet construct 300, and the retention elements 400. The leafletconstruct 300 is that portion of the valve 100 that comprises theleaflets 310 and the structure for coupling the leaflets 310 to theleaflet frame 200. In accordance with an embodiment, the leafletconstruct 300 defines a contiguous cylinder defining a plurality ofleaflets 310 and a bridge region 330 between each of the leaflets 310.Each bridge region defines a bridge first end 332 adjacent a firstleaflet 310 and a bridge second end 334 adjacent a second leaflet 310.The leaflets extend radially inward from the leaflet frame 200 whencoupled to the leaflet frame 200. Each of the leaflets 310 defines afold-over portion 324 that is folded over and lies against a leafletframe outer side 204 of the leaflet frame 200 and coupled thereto, suchas with securement structure, such as, but not limited to suture,adhesive, thermal bonding, or other means. Each of the bridge regions330 defines a bridge loop 338 with a coaptation neck 340 between thebridge loop 338 and the adjacent leaflets 310. The coaptation neck 340is operable to pass through one of the post slots 217 so that the bridgeloop 338 is adjacent to the outer portion of the leaflet frame 200 andthe leaflets 310 extend radially inward from the leaflet frame 200. Aretention element 400 is disposed within the bridge loop 338 effectivelypreventing the bridge loop 338 from passing through the post slot 217.The retention element 400 may be coupled to the commissure post 210,such as with suture, adhesive, thermal bonding, or other means. Thefold-over portion 324 of each of the leaflets 310 is folded around aninflow edge of the leaflet frame 200 and coupled thereto, such as withsuture, adhesive, thermal bonding, or other means.

In accordance with an embodiment, each bridge region 330 is wrappedaround a retention element outer side 412 to the retention element innerside 414 of one of the retention elements 400 with the bridge first end332 wrapped across the retention element inner side 414 to adjacent adividing line 416 that vertically bisects the retention element 400,from a first direction and the bridge second end 334 wrapped across theretention element inner side 414 to adjacent the dividing line 416 froman opposite direction, wherein the bridge first end 332 and bridgesecond end 334 are adjacent to each other to define a coaptation neck340.

In accordance with an embodiment, the leaflet frame assembly 234 isprovided with means for coupling to a native tissue annulus, and thusthe leaflet frame assembly 234 is a prosthetic heart valve 100. In anembodiment, a sewing cuff 600 is coupled to the leaflet frame assembly234, where the sewing cuff is operable to be sutured to the nativetissue annulus. In another embodiment, a base frame 500 comprising asewing cuff 600 is coupled to the leaflet frame assembly 234.

One possible way to characterize the benefits of some embodimentspresented herein is the effect of the bridge region 330 being acontinuous member, that is, no seams or breaks. Any force tending topull or extract the bridge region 330 through the post slot 217 iscountered by the tensile strength of the material that the bridge region330 comprises. The forces on the leaflets 310 during use are greatest atthe commissure posts 210 tending to pull the leaflets 310 away from thecommissure posts 210. The coupling of the leaflet construct 300 to theleaflet frame 200 at the commissure posts 210, in accordance with theseembodiments, does not rely solely on the suture 700 but also theretention element 400 that prevents the bridge region 330 from passingthrough the post slot 217. It is understood that sutures, in general,tend to loosen and fail over a period of time, especially in regions ofhigh stress. In these embodiments, the suture 700 that couples thebridge region 330 to the commissure post 210 may loosen or fail but theretention element 400 continues to prevent the bridge region 330 frompassing through the post slot 217 preventing failure of the valve 100.

Further, the retention element 400 provides a clamping force between aportion of the bridge region 330 and the post outer side 212 of thecommissure post 210 during operation of the valve 100. This clampingforce is the result of the retention element 400 being larger than thepost slot 217 which prevents the bridge region 330 from passing throughthe post slot 217. The clamping force does not rely on the strength ofthe suture 700 or the tension of the suture on the bridge region 330 andthe commissure posts 210.

This clamping force may tend to distribute the forces on the bridgingregion 330 reducing peak stresses that might be applied at the suture700 and apertures 999. Further the clamping force is the primary mode oftransferring the forces from the leaflets 130 to the leaflet frame 200rather than merely relying on the stitching of the leaflets 310 to theleaflet frame 200. Further, the angle alpha of the two loop fold lines336 allows for a substantially equal distribution of stresses over thecoaptation neck 340 between the bridge loop 338 and the adjacentleaflets 310 whereby reducing the peak stresses in the coaptation neck340.

In accordance with these embodiments, the leaflets 310 extendperpendicular from the leaflet frame 200, as shown in FIG. 5 . Theleaflets 310 extend from the post slot 217 in a direction perpendicularto the post inner side 214 As such, the leaflets 310 exhibit a biastoward the closed position. This is beneficial in that the valve 100will tend to close earlier during the phase of the cardiac cycle wherethe blood is decelerating or reversing. An earlier closure will tend toreduce back flow through the valve 100.

The design and manufacturing process (including the various componentsand the way of assembling those components) greatly reduce possiblestress concentration at the leaflet frame-leaflet junction bydistributing the load more evenly. These design and manufacturingprocess aspects also (1) reduce the burden of extensive and demandingsuturing, (2) increase the consistency of valve manufacturing results,and (3) increase the service life of a resulting valve as a consequenceof all of the foregoing factors.

Instead of or in addition to suture, chemical bonds and/or adhesives canbe used between the leaflet frame 200 and the fold-over portion 324 ofthe leaflet construct.

The bridge regions 330 are passed through the post slot 217 in a numberof ways. In accordance with an embodiment, the bridge region 330 isformed into a narrow bridge loop 338 which is passed through the postslot 217 from the leaflet frame inner side 202 to the leaflet frameouter side 204. A retention element 400 may then be inserted into thebridge loop 338 preventing the bridge loop 338 from being passed backthrough the post slot 217.

In accordance with embodiments, the leaflet frame 200, leaflet construct300 and the retention elements 400 have matching and radially alignedapertures for receiving suture. The fold-over portion 324 and the bridgeregions 330 containing a retention element 400 are coupled to theleaflet frame by suturing through these matching apertures. The dashedlines in FIG. 7 show an illustrative suture pattern. The suturingwork-load is very light and not skill-demanding.

Base Frame

The base frame 500 is a generally annular member defining a base framelumen 550 having a base frame inner side 502 and a base frame outer side504, as shown in FIGS. 3 and 4 . The base frame 500 may providestructural, load-bearing support to the leaflet frame 200. In addition,the base frame 500 can be configured to provide positive engagement tothe recipient tissue at the implantation site.

In accordance with an embodiment, the base frame 500 defines a pluralityof triangular regions 526 extending away from the base frame inflow edge520. The leaflet frame 200 may comprise corresponding triangularopenings 256 defined by two leaflet window sides 223 of adjacent leafletwindows 222 of the leaflet frame 200 define two sides of an isoscelestriangle on the leaflet frame inflow edge 220. The triangular openings256 are operable to receive the triangular regions 526 of the base frame500 therein.

The base frame 500 can comprise any metallic or polymeric material thatis generally biocompatible. For example, the base frame 500 can comprisea material, such as, but not limited to nitinol, cobalt-nickel alloy,stainless steel, and polypropylene, acetyl homopolymer, acetylcopolymer, ePTFE, other alloys or polymers, or any other biocompatiblematerial having adequate physical and mechanical properties to functionas described herein.

The base frame 500 can be etched, cut, laser cut, or stamped into a tubeor a sheet of material, with the sheet then formed into an annularstructure.

In accordance with embodiments, the base frame 500 can be configured toprovide positive engagement to an implant site. In an embodiment, thevalve 100 further includes a sewing cuff 600 coupled about the baseframe 500, as shown in FIGS. 1A and 1B, that is operable to acceptsuture so as to be sewn to a tissue orifice. It is understood thatconventional, surgical techniques to implant prosthetic valves can beused to implant the valve 100, in accordance with embodiments.

It is appreciated that other elements or means for coupling the valve100 to an implant site are anticipated. By way of example, but notlimited thereto, other means, such as mechanical and adhesive means maybe used to couple the valve 100 to a synthetic or biological conduit.

In another embodiment, the valve 100 further comprises a base frame 500,as shown in FIGS. 3 and 4 . The base frame 500 is coupled to a leafletframe inflow edge 220 of the leaflet frame 200. The base frame 500 isprovided with base frame apertures 508 that may be used to suture thebase frame 500 to the leaflet frame 200 using suture 700. An advantageof a separate leaflet frame 200 and base frame 500 is that they may havedifferent physical characteristics. By way of example, a relatively lessstiff leaflet frame 200 supporting the leaflets 310 can be more likelyto reduce the loading encountered by the opening and closing leaflets130 as compared to a stiffer leaflet frame 200. The leaflet frame 200having a relatively less stiff property may reduce leaflet accelerationsand reduce the closing stresses on the leaflets 310. Wherein the baseframe 500 may be more stiff which would be more suitable for suturing tothe native tissue orifice. The base frame 500 may resist the compressiveforces that may be encountered at the implant site, for example.

In embodiments of the valve 100, the inclusion of a base frame 500 and aleaflet frame 200 provides a means for providing different physicalproperties for each of the base frame 500 and the leaflet frame 200suitable for a particular purpose. In accordance with an embodiment, thebase frame 500 is stiffer as compared with the leaflet frame 200. Thebase frame 500, when engaged to the implant site, such as, but notlimited to a tissue orifice, is rigid enough to not significantly deformunder physiological loading.

The physical properties of the base frame 500 and the leaflet frame 200depends, in part, on the size, shape, thickness, and material propertyof the base frame 500 and the leaflet frame 200.

Stiff and stiffness, as used herein and as is commonly used inengineering, is a measure of the resistance to deformation given by abase. Stiff and stiffness is a function of, among other things, materialproperties, the shape of the object, and the boundary conditions on theobject. Stiffness of the leaflet frame 200 (see FIG. 1A) may be measuredby any number of methods known in the art. In accordance with onemethod, cables may be coupled to each of the three commissure posts 210and brought together so as to allow the cables to be pulledsimultaneously along the axis of the leaflet frame, with the leafletframe held by the base frame 500. The amount of force on the cablesrequired to deflect the three commissure posts toward the axis providesa measure of stiffness. The same may be done with the base frame 500with the cables coupled to three equally spaced points on the baseframe, such as an apex of the triangular region 526, as shown in FIG. 4.

Sewing Cuff

The valve 100 may be provided with a sewing cuff 600 adjacent the baseframe 500, as shown in FIGS. 1A and 1B. The sewing cuff 600 is operableto provide structure that receives suture for coupling to the implantsite. The sewing cuff 600 may comprise any suitable material, such as,but not limited to, double velour polyester and silicone. The sewingcuff 600 may be located circumferentially around the base frame 500 orperivalvular depending from the base frame 500. The sewing cuff 600 maycomprise a filler material, such as, but not limited to, a silicone ringand/or PTFE felt.

Methods

A method of making a prosthetic valve, in accordance with embodiment,comprises obtaining a tube comprising one or more layers of expandedPTFE composite. Cutting a leaflet construct including a plurality ofleaflets each being separated by a bridge region from the tube.Providing fold-over apertures in fold-over portions of the leaflets andbridge apertures in the bridge region. Obtaining a plurality ofretention elements, each retention element defining retention elementapertures. Folding each of the bridge regions into a bridge loop anddefining a coaptation neck between each bridge loop and two adjacentleaflets, the bridge loops extending radially away from the tube axis.Disposing a retention element into each of the bridge loops. Suturingeach retention element to the respective bridge loop passing suturethrough the bridge apertures and the retention element apertures thatare aligned therewith. Cutting a leaflet frame from a metal tubedefining leaflet frame windows and commissure posts therebetween whereeach commissure post defines a post slot dimensioned to receive a doublethickness of the bridge region. Providing leaflet window frame aperturesin the leaflet window frame and post apertures in the commissure posts.Disposing each coaptation neck in a respective post slot with theretention elements adjacent the post outer side and disposing theleaflets in the leaflet frame. Aligning the retention element apertureswith the post apertures. Suturing each retention element to therespective commissure post passing suture through the retention elementapertures and the post apertures that are aligned therewith. Folding thefold-over portions of each leaflet along the leaflet frame inflow edgeand against the leaflet frame outer side aligning the fold-overapertures with the leaflet window frame apertures. And suturing eachfold-over portion to the respective leaflet window frame passing suturethrough the fold-over apertures and the leaflet window frame aperturesthat are aligned therewith.

In accordance with an embodiment the method may further compriseproviding strips of fabric, wrapping and sewing the fabric on theleaflet frame to provide a cushion between the leaflet frame and theleaflet construct, and trimming the fabric to approximately 3 mm fromthe leaflet frame outflow edge of the leaflet frame.

In accordance with an embodiment the method may further comprise cuttinga base frame from a metal tube defining base frame apertures, andcoupling the base frame to the leaflet frame inflow edge of the leafletframe.

In accordance with an embodiment the method may further compriseproviding a fabric tube and inserting the fabric tube through the baseframe along its flow axis. Folding the fabric outflow edge of the fabricover the base frame outflow edge of the base frame. Sewing the fabricinto place using suture through the base frame apertures in the baseframe. Inverting the fabric inflow edge of the fabric tube over the baseframe. Sewing the fabric tube into place using suture through base frameapertures along the inflow edge of the base frame. Disposing a sewingcuff insert inside a pocket defined by the inverted fabric tube andtucking the fabric tube in between the base frame and the sewing cuffinsert such that all the slack of the fabric tube is removed around thesewing cuff. Placing the leaflet frame coaxially with and adjacent tothe base frame and inside the fabric tube. Trimming the fabric tubeapproximately 5 mm from the leaflet frame outflow edge and suturing theleaflet frame to the base frame at the leaflet window base using suturepassing through the respective leaflet window frame apertures and thebase frame apertures. Folding the trimmed edge of the fabric tube overthe leaflet frame outflow edge, tucking the trimmed edge underneathitself to conceal any frayed edges, and sewing the fabric tube to thefabric on the leaflet frame.

EXAMPLE

By way of example, one embodiment of a valve was made as follows:

A surgical prosthetic heart valve was constructed in the followingmanner. A leaflet construct 300, including fold-over apertures 308 andbridge apertures 309, was cut from the leaflet coupon using a CO2 laseraccording to the pattern shown in FIG. 3 .

Three retention elements 400 made from PEEK, shown in FIG. 3 , were sewnonto the bridge loop 338 of the bridge region 330 of the leafletconstruct 300, as shown in FIGS. 5 and 6 . The retention element 400 isprovided with retention element apertures 408 that align with bridgeapertures 309 on the leaflet construct 300. A partial view of theresulting assembly is shown in FIG. 2 .

A leaflet frame 200 and base frame 500 were laser cut, including leafletframe apertures 208 and base frame apertures 508, respectively, andelectropolished from a tube of cobalt chromium (MP35N) with a 25 mm ODand 0.4 mm wall thickness, as shown in FIG. 3 . The frames were cleanedin an ultrasonic bath of ethanol to remove contaminants. Three strips ofpolyester knit fabric were wrapped and sewn on the leaflet frame, toprovide a cushion between the leaflet frame 200 and the leafletconstruct 300. A post slot 217 of the commissure post 210 large enough(approximately 0.254 mm) to accommodate a double thickness of theleaflet construct 300 at the bridge region 330 was provided. Theremaining polyester knit fabric was trimmed off approximately 3 mm fromthe leaflet frame outflow edge 224 of the leaflet frame 200 shown inFIG. 4 . The leaflet construct 300 with retention elements 400 wasplaced onto the leaflet frame 200 by sliding each coaptation neck 340 inthe post slot 217 with the retention elements 400 on the post outer side212, as shown in FIG. 2 . The retention element apertures 408 werealigned with leaflet frame apertures 208 on the leaflet frame 200 andwere sewn into place with suture 700, as shown in FIG. 6 . The leafletconstruct 300 includes fold-over portions 324 and fold-over apertures308 along attachment edges. The fold-over portions 324 were folded alongthe leaflet frame inflow edge 220 of the leaflet frame 200 up againstthe leaflet frame outer side 204 where fold-over apertures 308 in thefold-over portions 324 coincide with leaflet frame apertures 208 of theleaflet frame 200 and were sewn into place with suture 700 as shown inFIG. 7 .

A tube of polyester knit fabric about 24 mm in diameter and at least 10cm in length was inserted through the base frame 500 along its flowaxis. The fabric outflow edge of the polyester knit fabric was foldedover the base frame outflow edge 524 of the base frame 500 and sewn intoplace using suture 700 through base frame apertures 508 in the baseframe 500 (not shown). The fabric inflow edge of the polyester knitfabric tube was inverted over the base frame 500 and sewn into placeusing suture 700 through base frame apertures 508 along the base frameinflow edge 520 of the base frame 500. A silicone sewing cuff insert wasplaced over the base frame 500 and inside of the inverted polyester knitfabric tube. The polyester knit fabric tube was tucked in between thebase frame 500 and the sewing cuff insert such that all the slack wasremoved around the sewing cuff 600.

The leaflet frame assembly 234 comprising the leaflet frame 200, theleaflet construct 300 and retention elements 400 was coaxially placedadjacent the base frame and inside the polyester knit fabric tube. Thepolyester knit fabric tube was trimmed approximately 5 mm off theleaflet frame outflow edge 224. The leaflet frame 200 was sutured to thebase frame 500 at the leaflet window base 225, with three sutures 700 ateach of the three leaflet window bases 225 of the leaflet frame 200. Thetrimmed edge of the polyester knit fabric was folded over the leafletframe outflow edge 224. The trimmed edge was tucked underneath itself toconceal any frayed edges and sewn to the polyester knit fabric on theleaflet frame.

Numerous characteristics and advantages have been set forth in thepreceding description, including various alternatives together withdetails of the structure and function of the devices and/or methods. Thedisclosure is intended as illustrative only and as such is not intendedto be exhaustive. It will be evident to those skilled in the art thatvarious modifications can be made, especially in matters of structure,materials, elements, components, shape, size and arrangement of partsincluding combinations within the principles of the disclosure, to thefull extent indicated by the broad, general meaning of the terms inwhich the appended claims are expressed. To the extent that thesevarious modifications do not depart from the spirit and scope of theappended claims, they are intended to be encompassed therein.

What is claimed:
 1. A method of making a prosthetic valve, the methodcomprising: cutting a leaflet construct from a tube of material suchthat the leaflet construct includes a plurality of leaflets eachseparated by a bridge region and having fold-over apertures in fold-overportions of each leaflet and bridge apertures in the bridge region;folding each of the bridge regions into a bridge loop, each bridge loopof the plurality of leaflets defining coaptation necks between thebridge loop and two adjacent leaflets of the plurality of leaflets;locating a retention element in each of the bridge loops; suturing eachretention element to the respective bridge loop by passing suturethrough the bridge apertures and respective retention element aperturesthat are aligned therewith; disposing each coaptation neck in arespective post slot of a leaflet frame that is a tube defining leafletframe windows and a plurality of commissure posts therebetween, whereeach of the plurality of commissure posts defines a post slotdimensioned to receive a double thickness of the tube at the bridgeregion and the leaflet frame has leaflet window frame apertures in theleaflet window frame and post apertures in the commissure posts;positioning the retention elements adjacent an outer side of arespective one of the commissure posts and disposing the leaflets in theleaflet frame; aligning the retention element apertures with the postapertures; suturing each retention element to the respective commissurepost passing suture through the retention element apertures and the postapertures that are aligned therewith; folding the fold-over portions ofeach leaflet along a leaflet frame inflow edge and against a leafletframe outer side aligning the fold-over apertures with the leafletwindow frame apertures; and suturing each fold-over portion to therespective leaflet window frame passing suture through the fold-overapertures and the leaflet window frame apertures that are alignedtherewith.
 2. The method of claim 1, wherein the tube of materialcomprises one or more layers of expanded PTFE composite.
 3. The methodof claim 1, further comprising: providing strips of fabric; wrapping andsewing the strips of fabric on the leaflet frame to provide a cushionbetween the leaflet frame and the leaflet construct; and trimming thestrips of fabric to adjacent a leaflet frame outflow edge of the leafletframe.
 4. The method of claim 3, further comprising: providing a baseframe that is a tube defining base frame apertures, the base framedefining a base frame central axis; placing the leaflet frame and baseframe in coaxial alignment; and coupling the base frame to the leafletframe inflow edge of the leaflet frame.
 5. The method of claim 4,further comprising: providing a fabric tube; inserting the fabric tubethrough the base frame along the base frame central axis; folding afabric outflow edge of the fabric tube over a base frame outflow edge ofthe base frame; coupling the fabric outflow edge to the base frame bysewing the fabric outflow edge using suture through the base frameapertures in the base frame; inverting a fabric inflow edge of thefabric tube over the base frame; coupling the fabric inflow edge to aninflow edge of the base frame by sewing the fabric inflow edge usingsuture through the base frame apertures that are adjacent the inflowedge of the base frame; disposing a sewing cuff insert inside a pocketdefined by the fabric tube that has been inverted; tucking the fabrictube in between the base frame and the sewing cuff insert such that allslack of the fabric tube is removed around the sewing cuff insert;placing the leaflet frame coaxially with and adjacent to the base frameand inside the fabric tube; trimming the fabric tube to adjacent aleaflet frame outflow edge; suturing the leaflet frame to the base frameat a leaflet window base using suture passing through the respectiveleaflet window frame apertures and the base frame apertures; folding atrimmed edge of the fabric tube over the leaflet frame outflow edge;tucking the trimmed edge underneath itself to conceal any frayed edges;and sewing the fabric tube to the strips of fabric on the leaflet frame.6. A method of making a prosthetic valve, the method comprising: forminga leaflet construct including a plurality of leaflets that arecontiguous with one another and are interconnected by a plurality ofbridge regions; folding each of the plurality of bridge regions into aplurality of bridge loops; passing each of the plurality of bridge loopsthrough a plurality of post slots in a plurality of commissure posts ofa leaflet frame; receiving a plurality of retention elements in theplurality of bridge loops such that each of the plurality of retentionelements is abutted against an outer side of the plurality of commissureposts of the leaflet frame; securing the plurality of bridge loops tothe plurality of retention elements, the plurality of retention elementsto the plurality of commissure posts, and the plurality of bridge loopsto the plurality of commissure posts; and folding portions of each ofthe plurality of leaflets over the leaflet frame to define a pluralityof fold-over portions and securing the fold-over portions in a foldedconfiguration to couple the fold-over portions to the leaflet frame. 7.The method of claim 6, further comprising using a plurality of suturesto secure the plurality of bridge loops to the plurality of retentionelements, the plurality of retention elements to the plurality ofcommissure posts, and the plurality of bridge loops to the plurality ofcommissure posts.
 8. The method of claim 6, further comprising using aplurality of sutures to secure the fold-over portions in the foldedconfiguration to couple the fold-over portions to the leaflet frame. 9.The method of claim 6, further comprising forming the leaflet constructincluding the plurality of leaflets that are contiguous with one anotherand are interconnected by the plurality of bridge regions by cutting atube of material into the leaflet construct.
 10. The method of claim 6,further comprising forming a plurality of apertures through each of theplurality of bridge regions, each of the plurality of commissure posts,and each of the plurality of retention elements locating a plurality ofsecurement structures in the plurality of apertures through each of theplurality of bridge regions, each of the plurality of commissure posts,and each of the plurality of retention elements to secure the pluralityof bridge regions, the plurality of commissure posts, and the pluralityof retention elements together.
 11. The method of claim 6, wherein theleaflet construct is formed of one or more layers of expanded PTFEcomposite.
 12. A method of implanting a prosthetic valve, the methodcomprising: positioning a prosthetic valve at an implant site in a bodyof a patient, the prosthetic valve including a leaflet frame, a leafletconstruct, and a retention element, the leaflet construct defining acylinder having a leaflet frame inner side and a leaflet frame outerside, the leaflet frame having a leaflet frame central axis and aplurality of commissure posts extending parallel to the leaflet framecentral axis that are spaced from one another, each commissure postdefining a post slot therethrough that is aligned parallel to theleaflet frame central axis, between the commissure posts and contiguoustherewith is a leaflet window, the leaflet construct defining acontinuous, uninterrupted cylinder comprising a plurality of leafletsand a bridge region seamlessly interconnecting each of the leaflets, theleaflets extending inward from the leaflet frame, each of the leafletsdefining a fold-over portion that is folded over and lies against theleaflet frame outer side of the leaflet frame and coupled thereto, eachof the bridge regions extending through one of the post slots anddefining a bridge loop that is adjacent to the leaflet frame outer side,and the retention element having a width that is larger than a width ofthe post slot, the retention element being disposed in the bridge loopand operable to prevent the bridge loop from passing through the postslot; and securing the prosthetic valve at the implant site in the bodyof the patient.
 13. The method of claim 12, further comprising securingthe prosthetic valve at the implant site in the body of the patient bysewing a sewing cuff of the prosthetic valve to tissue at the treatmentsite.
 14. The method of claim 12, wherein following implantation of theprosthetic valve at the implant site, blood flows into the valve past aninflow edge of the leaflet frame over which the fold-over portion ofeach of the leaflets is folded around.
 15. A method of implanting aprosthetic valve, the method comprising: positioning a prosthetic valveat an implant site in a body of a patient, the prosthetic valveincluding a leaflet frame, a leaflet construct, and a plurality ofretention elements, the leaflet frame defining a plurality of commissureposts each defined by a first post leg and a second post leg separatedby a post slot, the leaflet construct defining a continuous,uninterrupted cylinder including a plurality of leaflets and a pluralityof bridge regions seamlessly interconnecting each of the plurality ofleaflets, where each of the plurality of bridge region is folded into aloop, is received through one of the post slots of the plurality ofcommissure posts, and is wrapped around one of the plurality ofretention elements; and securing the prosthetic valve at the implantsite in the body of the patient.
 16. The method of claim 15, furthercomprising securing the prosthetic valve at the implant site in the bodyof the patient by sewing a sewing cuff of the prosthetic valve to tissueat the treatment site.
 17. The method of claim 15, wherein portions ofeach of the plurality of leaflets are folded over an inflow edge of theleaflet frame to define a plurality of fold-over portions and followingimplantation of the prosthetic valve at the implant site, blood flowsinto the valve past the inflow edge of the leaflet frame.